1. Field of the Invention
The present invention relates to a method for flattening a glass substrate.
2. Description of the Related Art
For example, very high flatness may be required of a glass substrate used as a component of a liquid crystal display panel. As a conventional method for flattening such a glass substrate, there is available a method which includes preparing two kinds of etching liquids different from each other in an etching rate for the glass substrate, first etching the substrate with the etching liquid at a fast etching rate, and then with the etching liquid at a slow etching rate, thereby flattening a surface of the glass substrate (e.g., US Pat. Appln. Publication No. 2006-0027535 A1).
According to the above conventional method for flattening the glass substrate, when the surface of the glass substrate initially has concave portions such as very small flaws, if etching is first carried out with the etching liquid at the fast etching rate, the concave portions are removed together with a surface layer of the glass substrate as the etching progresses fast. If etching is next carried out with the etching liquid at the slow etching rate, the surface of the glass substrate is flattened.
According to the conventional method for flattening the glass substrate, however, as the etching is first carried out with the etching liquid at the fast etching rate, and then with the etching liquid at the slow etching rate, there is a problem that flatness of the surface of the glass substrate is not so high for reasons described below.